1. Field of the Invention
The present invention relates to a semiconductor device including an internal circuit defined by an active area, a plurality of peripheral circuit units arranged on the peripheral of the internal circuit and a plurality of pads arranged on the peripheral of the internal circuit facing the peripheral circuit units.
2. Description of the Related Art
A typical semiconductor device is constructed by an internal circuit, a single row of peripheral circuit units connected to the internal circuit and arranged on at least one peripheral edge of the internal circuit such as input/output (I/O) circuit units, power supply circuit units and ground circuit units, a plurality of pads each connected to one of the peripheral circuit units.
As the multi-function and integration of semiconductor devices have been developed, the number of pads and the number of peripheral circuit units have been increased, so that the pitch of pads and the pitch of peripheral circuit units have been narrowed.
In order to substantially widen the pitch of pads, a first prior art semiconductor device is constructed by locating the pads in a zigzagged (staggered) arrangement (see: JP-11-87399-A and JP-2003-163267-A). This will be explained later in detail.
In the above-described first prior art semiconductor device, however, although the pitch of pads is substantially widened, the pitch of peripheral circuit units is never widened. As a result, when the number of the pads and the number of peripheral circuit units are increased, the width of each of the peripheral circuit units along the peripheral direction is decreased, so that the width of interconnections between the pads and the peripheral circuit units is decreased, which would limit current supplied from the pads to the peripheral circuit units and vice versa. Also, the width of interconnections between the peripheral circuit units and the internal circuit is decreased to limit currents supplied from the peripheral circuit units to the internal circuit and vice versa. Further, since the peripheral circuit units are very elongated, the flexibility of the layout design of transistor elements within the peripheral circuit units is limited.
Additionally, in order to compensate for the narrowed pitch of peripheral circuit units, a second prior art semiconductor device is constructed by locating all or part of pads immediately above the peripheral circuit units (see: JP-2003-163267-A). These pads are called circuit-under-pad (CUP) pads. This also will be explained later in detail.
Even the above-described second prior art semiconductor device has the same problems as the first prior art semiconductor device, although the area of the peripheral circuit units or the area of the internal circuit can be increased.